how to calculate this sym of serie?

z=q+q*(q-1)+q*(q-1)*(q-2)+...+q*(q-1)*(q-2)*...*(q-n)

Answer 1

[Image Analyst]

Try this intuitive, brute force method:

clc;
% Sample numbers:
q = 10;
n = 3;
theSum = 0;
for k = 0 : n
  qArray = q : -1 : q-k;
  p = prod(qArray)
  theSum = theSum + p;
end
% Print to command window
theSum

[N/A]

thnx a lot :)